I realised that my file server shares have all vanished. Checks revealled that the folders have become hidden and read-only and replacemenent exe's with the same name as the folders are not available instead.
My read around indicates this is Dropper virus or trojan. My antivirus program, Avira, could not detect this virus.
I would like a step by step manual way of removing this virus and restoring the files and folders on my server to their original status.